Sericin and swimming on histomorphometric parameters of denervated plantar muscle in Wistar rats

Abstract

ObjectiveTo analyze the combined effects of the silk protein sericin and swimming exercise on histomorphometry of the plantar muscle in Wistar rats.MethodsForty adult rats were randomly allocated into 5 groups comprising 8 animals each, as follows: Control, Injury, Sericin, Swim, and Swim plus Sericin. Three days after crushing of the sciatic nerve the rats in the Swim and Swim plus Sericin Groups were submitted to swimming exercise for 21 days. Rats were then euthanized and the plantar muscle harvested and processed.ResultsCross-sectional area, peripheral nuclei and muscle fiber counts, nucleus/fiber ratio and smallest muscle fiber width did not differ significantly between groups. Morphological analysis revealed hypertrophic fibers in the Swim Group and evident muscle damage in the Swim plus Sericin and Injury Groups. The percentage of intramuscular collagen was apparently maintained in the Swim Group compared to remaining groups.ConclusionCombined treatment with sericin and swimming exercise did not improve muscle properties. However, physical exercise alone was effective in maintaining intramuscular connective tissue and preventing progression of deleterious effects of peripheral nerve injury.

Comparação de diferentes comprimentos de onda do laser de baixa potência no sóleo de ratos Wistar após lesão nervosa

“…Based on the morphological analysis, it was possible to notice that G2, G3, and G4 underwent characteristic changes of muscle injury and that there was no return to normal muscle properties compared to the control group. The normal morphology of muscle fibers is described as multinucleated polygonal cells, with the nuclei positioned in the periphery 1,17 , similar to what was found in the control group. In the nerve-damaged groups, some cells with amorphous shape and globose nuclei were found, some of them inside the sarcoplasmic membrane.…”

“…Regarding morphometric analysis, by the measurements of area and smaller diameter, it is evident that all injury groups presented atrophy of muscle fibers. Santana et al 1,15 observed, in a similar model of nerve injury, muscle fibers characteristics of tropism, with reduction in strength and phenotypic changes. In our study, only the group using 830 nm obtained a higher result than the injury group for the area of muscle fibers, observing a small evolution.…”

“…Recovery from peripheral nerve injury is repeatedly assessed by functional tests 8 , and, as one of the main effects of this injury is precisely on skeletal muscle tissue 1 , this study aimed to compare two wavelengths of LLLT in morphological characteristics of muscle tissue recovery after sciatic nerve compression, although none of the wavelengths tested has produced this recovery, presenting muscle fibers with morphological characteristics similar to the control group without injury. Only slightly better results were observed for the group that used the 830 nm wavelength, regarding the area of muscle fiber.…”

“…As a consequence, the transmission of nerve impulses is interrupted, which causes a decrease or loss of sensitivity and motor function of the innervated area. Due to its location and extension, the sciatic nerve is predisposed to lesions that affect the muscle tissue related to its path, with fiber atrophy and structural changes that impair motor functions of lower limbs 1,2 .…”

Muscle preservation in proximal nerve injuries: a current update

“…There is currently no consensus on the optimal use of kinesiotherapy. The most recent and popular methods that have demonstrated a positive effect of preserving and increasing muscle mass in conditions associated with the impossibility of voluntary contraction (peripheral nerve or spinal cord injuries) and degenerative changes leading to atrophy (senile sarcopenia) are passive repetitive muscle stretching (Wang et al., 2021), passive training (Shiyang et al., 2020), passive locomotor training (Hadj-Saïd et al., 2012), range of motion exercises (Rahiminezhad et al., 2022), resistance training (Messi et al., 2016), high-intensity interval training (Tayebi et al., 2019) and swimming (Santana et al., 2018). These are home-based protocols with varying frequencies, from once to twice a week, three to four times a week, to daily sessions.…”